Dehydrogenation method using sulfided nonacidic multimetallic catalyst

ABSTRACT

Dehydrogenatable hydrocarbons are dehydrogenated by contacting them at dehydrogenation conditions, with a sulfided nonacidic multimetallic catalytic composite comprising a combination of catalytically effective amounts of a platinum or palladium component, an iridium component, a tin or lead component, an alkali or alkaline earth component and a sulfur component with a porous carrier material. This sulfided nonacidic multimetallic catalytic composite has the metallic components uniformly dispersed throughout the porous carrier material, the platinum or palladium and iridium components in the sulfided state or in a mixture of the elemental metallic state and the sulfided state, and the alkali or alkaline earth and tin or lead components in an oxidation state above the elemental metal. This composite has been sulfided, moreover, prior to use in the dehydrogenation method and after the platinum or palladium and iridium components thereof have been reduced to the elemental metallic state.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of my prior, copendingapplication Ser. No. 535,078 filed Dec. 20, 1974; now U.S. Pat. No.3,980,726, issued Sept. 14, 1976 which in turn is a continuation-in-partof my prior application Ser. No. 365,877 filed June 1, 1973, and nowU.S. Pat. No. 3,856,870; and which in turn is a continuation-in-part ofmy prior, now abandoned application Ser. No. 27,457 filed Apr. 10, 1970.A related application is Ser. No. 647,461 filed Jan. 8, 1976, now U.S.Pat. No. 4,003,852 issued Jan. 18, 1977. All of the teachings of theseprior applications are specifically incorporated herein by reference.

The subject of the present invention is, broadly, an improved method fordehydrogenating a dehydrogenatable hydrocarbon to produce a hydrocarbonproduct containing the same number of carbon atoms but fewer hydrogenatoms. In another aspect, the present invention involves a method ofdehydrogenating normal paraffin hydrocarbons containing 4 to 30 carbonatoms per molecule to the corresponding normal mono-olefin with minimumproduction of side products. In yet another aspect, the presentinvention relates to a novel sulfided nonacidic multimetallic catalyticcomposite comprising a combination of catalytically effective amounts ofa platinum or palladium component, an iridium component, a tin or leadcomponent, a sulfur component and an alkali or alkaline earth componentwith a porous carrier material. This composite has highly beneficialcharacteristics of activity, selectively, and stability when it isemployed in the dehydrogenation of dehydrogenatable hydrocarbons such asaliphatic hydrocarbons, naphthene hydrocarbons, and alkylaromatichydrocarbons.

The conception of the present information followed from my search for anovel catalytic composite possessing a hydrogenation-dehydrogenationfunction, a controllable cracking function, and superior conversion,selectivity and stability characteristics when employed in hydrocarbonconversion processes that have traditionally utilized dual-functioncatalytic composites. In my prior applications I disclosed a significantfinding with respect to a nonacidic multimetallic catalytic compositemeeting these requirements. More specifically, I determined that acombination of specified amounts of iridium and tin or lead can beutilized, under certain conditions, to beneficially interact with theplatinum or palladium component of a nonacidic catalyst with a resultingmarked improvement in the performance of such a catalyst. Now I haveascertained that a sulfided nonacidic multimetallic catalytic composite,comprising a combination of catalytically effective amounts of aplatinum or palladium, iridium, sulfur, tin or lead, and an alkali oralkaline earth metal with a porous carrier material can have superioractivity, selectively, and stability characteristics when it is employedin a hydrocarbon dehydrogenation process if the metallic components areuniformly dispersed in the porous carrier material in the amountsspecified hereinafter, if the oxidation state of the metallicingredients are carefully controlled to be in the states hereinafterspecified and if the composite has been sulfided in the manner indicatedherein before use in the dehydrogenation of hydrocarbons and aftersubstantially all of the platinum or palladium and iridium componentsare reduced to the corresponding elemental metallic state.

The dehydrogenation of dehydrogenatable hydrocarbons is an importantcommercial process because of the great and expanding demand fordehydrogenated hydrocarbons for use in the manufacture of variouschemical products such as detergents, plastics, synthetic rubbers,pharmaceutical products, high octane gasolines, perfumes, drying oils,ionexchange resins, and various other products well known to thoseskilled in the art. One example of this demand is in the manufacture ofhigh octane gasoline by using C₃ and C₄ mono-olefins to alkylateiso-butane. Another example of this demand is in the area ofdehydrogenation of normal paraffin hydrocarbons to produce normalmono-olefins having 4 to 30 carbon atoms per molecule. These normalmono-olefins can, in turn, be utilized in the synthesis of a vast numberof other chemical products. For example, derivatives of normalmono-olefins have become of substantial importance to the detergentindustry whereby they are utilized to alkylate an aromatic, such asbenzene, with subsequent transformation of the product arylalkane into awide variety of biodegradable detergents such as the alkylaryl sulfonatetypes of detergents which are most widely used today for household,industrial, and commercial purposes. Still another large class ofdetergents produced from these normal mono-olefins are the oxy-alkylatedphenol derivatives in which the alkyl phenol base is prepared by thealkylation of phenol with these normal mono-olefins. Still another typeof detergents produced from these normal mono-olefins are thebiodegradable alkylsulfonates formed by the direct sulfation of thenormal mono-olefins. Likewise, the olefin can be subjected to directsulfonation with sodium bisulfite to make biodegradable alkylsulfonates.As a further example, these mono-olefins can be hydrated to producealcohols which then, in turn, can be used to produce plasticizers and/orsynthetic lube oils.

Regarding the use of products made by the dehydrogenation ofalkylaromatic hydrocarbons, they find wide application in the petroleum,petrochemical, pharmaceutical detergent, plastic, and the likeindustries. For example, ethylbenzene is dehydrogenated to producestyrene which is utilized in the manufacture of polystyrene plastics,styrene-butadiene rubber, and the like products. Isopropylbenzene isdehydrogenated to form alpha-methylstyrene which, in turn, isextensively used in polymer formation and in the manufacture of dryingoils, ion exchange resins, and the like materials.

Responsive to this demand for these dehydrogenation products, the arthas developed a number of alternative methods to produce them incommercial quantities. One method that is widely utilized involves theselective dehydrogenation of a dehydrogenatable hydrocarbon bycontacting the hydrocarbon with a suitable catalyst at dehydrogenationconditions. As is the case with most catalytic procedures, the principalmeasure of effectiveness for this dehydrogenation method involves theability to perform its intended function with minimum interference ofside reactions for extended periods of time. The analytical terms usedin the art to broadly measure how well a particular catalyst performsits intended functions in a particular hydrocarbon conversion reactionare activity, selectivity, and stability, and for purposes of discussionhere, these terms are generally defined for a given reactant as follows:(1) activity is a measure of the catalyst's ability to convert thehydrocarbon reactant into products at a specified severity level whereseverity level means the specific reaction conditions used -- that is,the temperature, pressure, contact time, and presence of diluents suchas H₂ ; (2) selectivity usually refers to the amount of desired productor products obtained relative to the amount of the reactant charged orconverted; (3) stability refers to the rate of change with time of theactivity and selectivity parameters -- obviously the smaller rateimplying the more stable catalyst. More specifically, in adehydrogenation process, activity commonly refers to the amount ofconversion that takes place for a given dehydrogenatable hydrocarbon ata specified severity level and is typically measured on the basis ofdisappearance of the dehydrogenatable hydrocarbon; selectivity istypically measured by the amount, calculated on a mole percent ofconverted dehydrogenatable hydrocarbon basis, of the desireddehydrogenated hydrocarbon obtained at the particular activity orseverity level; and stability is typically equated to the rate of changewith time of activity as measured by disappearance of thedehydrogenatable hydrocarbon and of selectivity as measured by theamount of desired dehydrogenated hydrocarbon produced. Accordingly, themajor problem facing workers in the hydrocarbon dehydrogenation art isthe development of a more active and selective catalytic composite thathas good stability characteristics.

I have now found a sulfided nonacidic multimetallic catalytic compositewhich possesses improved activity, selectivity, and stability when it isemployed in a process for the dehydrogenation of dehydrogenatablehydrocarbons. In particular, I have determined that the use of asulfided nonacidic multimetallic catalyst, comprising a combination ofcatalytically effective amounts of a platinum or palladium component, aniridium component, a tin or lead component, an alkali or alkaline earthcomponent and a sulfur component with a porous refractory carriermaterial, can enable the performance of a dehydrogenation process to besubstantially improved if the metallic components are uniformlydispersed throughout the carrier material in the amounts specifiedhereinafter, if their oxidation states are carefully controlled to be inthe states hereinafter specified and if the catalyst is properlysulfided before use in the instant dehydrogenation method. Particularlygood results are, moreover, obtained with this composite when it isutilized to produce dehydrogenated hydrocarbons containing the samecarbon structure as the reactant hydrocarbon but fewer hydrogen atoms.This sulfided nonacidic multimetallic composite is particularly usefulin the dehydrogenation of long chain normal paraffins to produce thecorresponding normal mono-olefin with minimization of side reactionssuch as demethylation, skeletal isomerization, aromatization,polymerization, cracking and polyolefin formation.

It is, accordingly, one object of the present invention to provide anovel method for the dehydrogenation of dehydrogenatable hydrocarbonsutilizing a sulfided nonacidic multimetallic catalytic compositecomprising a platinum or palladium component, an iridium component, atin or lead component, an alkali or alkaline earth component and asulfur component combined with a porous carrier material. A secondobject is to provide a novel nonacidic multimetallic catalytic compositehaving superior performance characteristics when utilized in ahydrocarbon dehydrogenation process. Another object is to provide animproved method for the dehydrogenation of normal paraffin hydrocarbonsto produce normal mono-olefins which method minimizes undesirable sidereactions such as demethylation, cracking, skeletal isomerization,polyolefin formation, polymerization and aromatization.

In brief summary, one embodiment of the present invention comprehends asulfided nonacidic multimetallic catalytic composite comprising a porouscarrier material having uniformly dispersed therein catalyticallyeffective amounts of a platinum or palladium component, an iridiumcomponent, a tin or lead component, an alkali or alkaline earthcomponent and a sulfur component. These components are preferablypresent in amounts sufficient to result in the catalytic compositecontaining, on an elemental basis, about 0.01 to about 2 wt. % platinumor palladium, about 0.1 to about 5 wt. % of the alkali metal or alkalineearth metal, about 0.01 to about 2 wt. % iridium, about 0.01 to about 5wt. % tin or lead and about 0.01 to about 1 wt. % sulfur. In addition,substantially all of the platinum or palladium and iridium componentsare present in the sulfided state or in a mixture of the elementalmetallic state and the sulfided state, and substantially all of the tinor lead and alkali or alkaline earth components are present in anoxidation state above that of the elemental metal. The sulfiding of thecomposite is performed prior to contact with the dehydrogenatablehydrocarbon and after substantially all of the platinum or palladium andiridium components have been reduced to the elemental metallic state bytreatment with a sulfiding gas at sulfiding conditions effective toincorporate about 0.01 to about 1 wt. % sulfur.

Another embodiment pertains to a method for dehydrogenating adehydrogenatable hydrocarbon which comprises contacting the hydrocarbonwith the sulfided nonacidic multimetallic catalytic composite describedin the first embodiment at dehydrogenation conditions.

Other objects and embodiments of the present invention involve specificdetails regarding essential and preferred catalytic ingredients,preferred amounts of ingredients, suitable methods of multimetalliccomposite preparation, suitable dehydrogenatable hydrocarbons, operatingconditions for use in the dehydrogenation process, and the likeparticulars. These are hereinafter given in the following detaileddiscussion of each of these facets of the present invention. It is to benoted that the term "nonacidic" means that the catalyst produces lessthan 10% conversion of 1-butene to isobutylene when tested atdehydrogenation conditions and, preferably, less than 1%.

Regarding the dehydrogenatable hydrocarbon that is subjected to themethod of the present invention, it can, in general, be an organiccompound having 2 to 30 carbon atoms per molecule and containing atleast one pair of adjacent carbon atoms having hydrogen attachedthereto. That is, it is intended to include within the scope of thepresent invention, the dehydrogenation of any organic compound capableof being dehydrogenated to produce products containing the same numberof carbon atoms but fewer hydrogen atoms, and capable of being vaporizedat the dehydrogenation temperatures used herein. More particularly,suitable dehydrogenatable hydrocarbons are: aliphatic compoundscontaining 2 to 30 carbon atoms per molecule, alkylaromatic hydrocarbonswhere the alkyl group contains 2 to 6 carbon atoms, and naphthenes oralkyl-substituted naphthenes. Specific examples of suitabledehydrogenatable hydrocarbons are: (1) alkanes such as ethane, propane,n-butane, isobutane, n-pentane, isopentane, n-hexane, 2-methylhexene,2-methylpentane, 2,2-dimethylbutane, n-heptane, 2-ethylhexane2,2,3-trimethylbutane, and the like compounds; (2) naphthenes such ascyclopentane, cyclohexane, methylcyclopentane, ethylcyclopentane,n-propylcyclopentane, 1,3-dimethylcyclohexane, and the like compounds;and (3)alkylaromatics such as ethylbenzene, n-butylbenzene,1,3,5-triethylbenzene, isopropylbenzene, isobutylbenzene,ethylnaphthalene, and the like compounds.

In a preferred embodiment, the dehydrogenatable hydrocarbon is a normalparaffin hydrocarbon having about 4 to 30 carbon atoms per molecule. Forexample, normal paraffin hydrocarbons containing about 10 to 18 carbonatoms per molecule are dehydrogenated by the subject method to producethe corresponding normal mono-olefin which can, in turn, be alkylatedwith benzene and sulfonated to make alkylbenzene sulfonate detergentshaving superior biodegradability. Likewise, n-alkanes having 10 to 18carbon atoms per molecule can be dehydrogenated to the correspondingnormal mono-olefin which, in turn, can be sulfonated or sulfated to makeexcellent detergents. Similarly, n-alkanes having 6 to 10 carbon atomscan be dehydrogenated to form the corresponding mono-olefin which can,in turn, be hydrated to produce valuable alcohols. Preferred feedstreams for the manufacture of detergent intermediates contain a mixtureof 4 or 5 adjacent normal paraffin homologues such as C₁₀ to C₁₃, C₁₁ toC₁₄, C₁₁ to C₁₅ and the like mixtures.

The sulfided nonacidic multimetallic catalyst used in the presentinvention comprises a porous carrier material or support having combinedtherewith a uniform dispersion of catalytically effective amounts of aplatinum or palladium component, an iridium component, a tin or leadcomponent, a sulfur component, and an alkali or alkaline earthcomponent.

Considering first the porous carrier material utilized in the presentinvention, it is preferred that the material be a porous, adsorptive,high-surface area support having a surface area of about 25 to about 500m² /g. The porous carrier material should be relatively refractory tothe conditions utilized in the dehydrogenation process, and it isintended to include within the scope of the present invention carriermaterials which have traditionally been utilized in dual-functionhydrocarbon conversion catalysts, such as: (1)activated carbon, coke,charcoal; (2) silica or silica gel, silicon carbide, clays, andsilicates including those synthetically prepared and naturallyoccurring, which may or may not be acid treated, for example, attapulgusclay, china clay, diatomaceous earth, fuller's earth, kaolin,kieselguhr, etc.; (3) ceramics, porcelain, crushed firebrick, bauxite;(4) refractory inorganic oxides such as alumina, titanium dioxide,zirconium dioxide, chromium oxide, zinc oxide, magnesia, thoria, boria,silica-alumina, silica-magnesia, chromia-alumina, aluminaboria,silica-zirconia, etc.; (5) crystalline zeolitic aluminosilicates such asnaturally occurring or synthetically prepared mordenite and/orfaujasite, either in the hydrogen form or in a form which has beentreated with multivalent cations; (6) spinels such as MgA1₂ O₄, FeA1₂O₄,ZnA1₂ O₄, MnA1₂ O₄, CaA1₂ O₄, and other like compounds having theformula MO·A1₂ O₃ where M is a metal having a valence of 2; and (7)combinations of elements from one or more of these groups. The preferredporous carrier material for use in the present invention are refractoryinorganic oxides, with best results obtained with an alumina carriermaterial. Suitable alumina materials are the crystalline aluminas knownas the gamma-, eta-, and thetalumina, with gamma- or eta-alumina givingbest results. In addition, in some embodiments the alumina carriermaterial may contain minor proportions of other well-known refractoryinorganic oxides such as silica, zirconia, magnesia, etc.; however, thepreferred support is substantially pure gamma- or eta-alumina. Preferredcarrier materials have an apparent bulk density of about 0.2 to about0.7 g/cc and surface area characteristics such that the average porediameter is about 20 to about 300 Angstroms, the pore volume is about0.1 to about 1 cc/g and the surface area is about 100 to about 500 m²/g. In general, best results are typically obtained with a gamma-aluminacarrier material which is used in the form of spherical particleshaving: a relatively small diameter (i.e. typically about 1/16 inch), anapparent bulk density of about 0.2 to about 0.6 (most preferably about0.3) g/cc, a pore volume of about 0.4 cc/g, and a surface area of about150 to about 200 m² /g.

The preferred alumina carrier material may be prepared in any suitablemanner and may be synthetically prepared or natural occurring. Whatevertype of alumina is employed, it may be activated prior to use by one ormore treatments including drying, calcination, steaming, etc., and itmay be in a form known as activated alumina, activated alumina ofcommerce, porous alumina, alumina gel, etc. For example, the aluminacarrier may be prepared by adding a suitable alkaline reagent, such asammonium hydroxide to a salt of aluminum such as aluminum chloride,aluminum nitrate, etc., in an amount to form an aluminum hydroxide gelwhich upon drying and calcining is converted to alumina. The aluminacarrier may be formed in any desired shape such as spheres, pills,cakes, extrudates, powders, granules, etc., and utilized in any desiredsize. For the purpose of the present invention, a particularly preferredform of alumina is the sphere; and alumina spheres may be continuouslymanufactured by the well-known oil drop method which comprises: formingan alumina hydrosol by any of the techniques taught in the art andpreferably by reacting aluminum metal with hydrochloric acid, combiningthe resulting hydrosol with a suitable gelling agent and dropping theresultant mixture into an oil bath maintained at elevated temperatures.The droplets of the mixture remain in the oil bath until they set andform hydrogel spheres. The spheres are then continuously withdrawn fromthe oil bath and typically subjected to specific aging treatments in oiland an ammoniacal solution to further improve their physicalcharacteristics. The resulting aged and gelled particles are then washedand dried at a relatively low temperature of about 300° F. to about 400°F. and subjected to a calcination procedure at a temperature of about850° F. to about 1300° F. for a period of about 1 to about 20 hours. Itis a good practice to subject the calcined particles to a hightemperature treatment with steam in order to remove undesired acidiccomponents such as residual chloride. This procedure effects conversionof the alumina hydrogel to the corresponding crystalline gamma-alumina.See the teachings of U.S. Pat. No. 2,620,314 for additional details.

One essential constituent of the instant multimetallic catalyticcomposite is the tin or lead component. It is an essential feature ofthe present invention that substantially all of the tin or leadcomponent is present in the final catalyst in an oxidation state abovethat of the elemental metal. In other words, this component may bepresent in chemcial combination with one or more of the otheringredients of the composite, or as a chemical compound of tin or leadsuch as the oxide, sulfide, halide, oxyhalide, oxychloride, aluminate,and the like compounds. Based on the evidence currently available, it isbelieved that best results are obtained when substantially all of thetin or lead component exists in the final composite in the form of thecorresponding oxide such as the tin oxide or lead oxide, and thesubsequently described oxidation, reduction and sulfiding steps, thatare preferably used in the preparation of the instant composite, arebelieved to result in the catalytic composite which contains an oxide ofthe tin or lead component. Regardless of the state in which thiscomponent exists in the composite, it can be utilized therein in anyamount which is catalytically effective, with the preferred amount beingabout 0.01 to about 5 wt. % thereof, calculated on an elemental basisand the most preferred amount being about 0.05 to about 2 wt. %. Theexact amount selected within this broad range is preferably determinedas a function of the particular metal that is utilized. For instance, inthe case where this component is lead, it is preferred to select theamount of this component from the low end of this range 13 namely, about0.01 to about 1 wt. %. Additionally, it is preferred to select theamount of lead as a function of the amount of the platinum groupcomponent as explained hereinafter. On the other hand, where thiscomponent is tin, it is preferred to select from a relatively broaderrange of about 0.05 to about 2 wt. % thereof. It is to be understoodthat mixtures of tin and lead are intended to be included within thescope of the expression "tin or lead component".

This tin or lead component may be incorporated in the composite in anysuitable manner known to the art to result in a uniform dispersion ofthe tin or lead moiety throughout the carrier material such as,coprecipitation or cogelation with the porous carrier material, ionexchange with the carrier material, or impregnation of the carriermaterial at any stage in its preparation. It is to be noted that it isintended to include within the scope of the present invention allconventional procedures for incorporating a metallic compound in acatalytic composite, and the particular method of incorporation used isnot deemed to be an essential feature of the present invention so longas the tin or lead component is uniformly distributed throughout theporous carrier material. One acceptable method of incorporating the tinor lead component into the catalytic composite involves cogelling thetin or lead component during the preparation of the preferred carriermaterial, alumina. This method typically involves the addition of asuitable soluble compound of the tin or lead to the alumina hydrosol.The resulting mixture is then commingled with a suitable gelling agent,such as a relatively weak alkaline reagent, and the resulting mixture isthereafter preferably gelled by dropping into a hot oil bath asexplained hereinbefore. After aging, drying, and calcining the resultingparticles there is obtained an intimate combination of the oxide of thetin or lead and alumina. One preferred method incorporating thiscomponent into the composite involves utilization of a solubledecomposable compound of the tin or lead to impregnate the porouscarrier material either before, during, or after the carrier material iscalcined. In general, the solvent used during this impregnation step isselected on the basis of its capability to dissolve the desired tin orlead compound without affecting the porous carrier material which is tobe impregnated; ordinarily, good results are obtained when water is thesolvent; thus the preferred tin or lead compounds for use in thisimpregnation step are typically water-soluble and decomposable. Examplesof suitable tin or lead compounds are: ammonium chlorostannate, tindichloride, tin tetrachloride, tin dibromide, tin dibromide di-iodide,tin tetrafluoride, tin tetraiodide, tin sulfate, tin tartrate, diethyltin dichloride, lead diacetate, lead dibromate, lead dibromide, leaddichlorate, lead dichloride, lead dicitrate, lead diformate, leaddilactate, lead malate, lead dinitrate, lead nitrite, lead dithionate,and the like compounds. In the case of tin, tin di- or tetra-chloridedissolved in water is preferred. In the case of lead, lead nitratedissolved in water is preferred. Regardless of which impregnationsolution is utilized, the tin or lead component can be impregnatedeither prior to, simultaneously with, or after the other metalliccomponents are added to the carrier material. Best results areordinarily obtained when the tin or lead component is tin oxide.

Regardless of which tin or lead compound is used in the preferredimpregnation step, it is essential that the tin or lead component beuniformly distributed throughout the carrier material. In oder toachieve this objective when this component is incorporated byimpregnation, it is necessary to maintain the pH of the impregnationsolution at a relatively low level corresponding to about 7 to about 1or less and to dilute the impregnation solution to a volume which is atleast approximately the same or greater than the void volume of thecarrier material which is impregnated. It is preferred to use a volumeratio of impregnation solution to carrier material of at least 1:1 andpreferably about 2:1 to about 10:1 or more. Similarly, it is preferredto use a relatively long contact time during the impregnation stepranging from about 1/4 hour up to about 1/2 hour or more before dryingto remove excess solvent in order to insure a high dispersion of the tinor lead component in the carrier material. The carrier material is,likewise preferably constantly agitated during this preferredimpregnation step.

A second essential ingredient of the subject catalyst is the platinum orpalladium component. That is, it is intended to cover the use ofplatinum or palladium or mixtures thereof as a second component of thepresent composite. It is an essential feature of the present inventionthat substantially all of this platinum or palladium component existswithin the final catalytic composite in a sulfided state or in a mixtureof the elemental metallic state and the sulfided state. Generally, theamount of this component present in the final catalyst composite issmall compared to the quantities of the other components combinedtherewith. In fact, the platinum or palladium component generally willcomprise about 0.01 to about 2 wt. % of the final catalytic composite,calculated on an elemental basis. Excellent results are obtained whenthe catalyst contains about 0.05 to about 1 wt. % of platinum orpalladium metal.

This platinum or palladium component may be incorporated in thecatalytic composite in any suitable manner known to result in arelatively uniform distribution of this component in the carriermaterial such as coprecipitation or cogelation, ion exchange orimpregnation. The preferred method of preparing the catalyst involvesthe utilization of a soluble, decomposable compound of platinum orpalladium to impregnate the carrier material in a relatively uniformmanner. For example, this component may be added to the support bycommingling the latter with an aqueous solution of chloroplatinic orchloropalladic acid. Other water-soluble compounds of platinum orpalladium may be employed in impregnation solutions and include ammoniumchloroplatinate, bromoplatinic acid, platinum trichloride, platinumtetrachloride hydrate, platinum dichlorocarbonyl dichloride,dinitrodiaminoplatinum, sodium tetranitroplatinate (II), palladiumchloride, palladium nitrate, palladium sulfate, diamminepalladium(II)hydroxide, tetramminepalladium (II) chloride, etc. The utilizationof a platinum or palladium chloride compound, such as chloroplatinic orchloropalladic acid, is ordinarily preferred. Hydrogen chloride, nitricacid or the like acid is also generally added to the impregnationsolution in order to further facilitate the uniform distribution of themetallic components throughout the carrier material. In addition, it isgenerally preferred to impregnate the carrier material after it has beencalcined or oxidized in order to minimize the risk of washing away thevaluable platinum or palladium compounds; however, in some cases it maybe advantageous to impregnate the carrier material when it is in agelled state.

A third essential ingredient of the present catalytic composite is aniridium component. It is of fundamental importance that substantiallyall of the iridium component exists within the catalytic composite ofthe present invention in the sulfided state or in a mixture of thesulfided state and the elemental state and the subsequently describedreduction and sulfiding procedure is designed to accomplish thisobjective. The iridium component may be utilized in the composite in anyamount which is catalytically effective, with the preferred amount beingabout 0.01 to about 2 wt. % thereof, calculated on an elemental iridiumbasis. Typically best results are obtained with about 0.05 to about 1wt. % iridium It is, additionally, preferred to select the specificamount of iridium from within this broad weight range as a function ofthe amount of the platinum or palladium component, on an atomic basis,as is explained hereinafter.

This iridium component may be incorporated into the catalytic compositein any suitable manner known to those skilled in the catalystformulation art which results in a relatively uniform dispersion ofiridium in the carrier material. In addition, it may be added at anystage of the preparation of the composite -- either during preparationof the carrier material or thereafter -- and the precise method ofincorporation used is not deemed to be critical. However, best resultsare thought to be obtained when the iridium component is relativelyuniformly distributed throughout the carrier material, and the preferredprocedures are the ones known to result in a composite having thisrelatively uniform distribution. One acceptable procedure forincorporating this component into the composite involves cogelling orcoprecipitating the iridium component during the preparation of thepreferred carrier material, alumina. This procedure usually comprehendsthe addition of a soluble, decomposable compound of iridium such asiridium tetrachloride to the alumina hydrosol before it is gelled. Theresulting mixture is then finished by conventional gelling, aging,drying, and calcination steps as explained hereinbefore. A preferred wayof incorporating this component is an impregnation step wherein theporous carrier material is impregnated with a suitableiridium-containing solution either before, during, or after the carriermaterial is calcined. Preferred impregnation solutions are aqueoussolutions of water soluble, decomposable iridium compounds, such asiridium tribromide, iridium dichloride, iridium tetrachloride, iridiumoxalic acid, iridium sulfate, potassium iridochloride, chloroiridicacid, sodium hexanitroiridate (III), and the like compounds. Bestresults are ordinarily obtained when the impregnation solution is anaqueous solution of chloroiridic acid or sodium chloroiridate. Thiscomponent can be added to the carrier material, either prior to,simultaneously with, or after the other metallic components are combinedtherewith. Best results are usually achieved when this component isadded simultaneously with the platinum or palladium components.

Yet another essential ingredient of the catalyst used in the presentinvention is the alkali or alkaline earth component. More specifically,this component is selected from the group consisting of the compounds ofthe alkali metals -- cesium, rubidium, potassium, sodium, and lithium --and of the alkaline earth metals -- calcium, strontium, barium, andmagnesium. This component exists within the catalytic composite in anoxidation state above that of the elemental metal such as a relativelystable compound such as the oxide or sulfide, or in combination with oneor more of the other components of the composite, or in combination withthe carrier material such as, for example, in the form of an alkali oralkaline earth metal aluminate. Since, as is explained hereinafter, thecomposite containing the alkali or alkaline earth component is alwayscalcined or oxidized in an air atmosphere before use in the conversionof hydrocarbons, the most likely state this component exists in duringuse in the dehydrogenation reaction is the corresponding metallic oxidesuch as lithium oxide, potassium oxide, sodium oxide, and the like.Regardless of what precise form in which it exists in the composite, theamount of this component utilized is preferably selected to provide anonacidic composite containing about 0.01 to about 5 wt. % of the alkalimetal or alkaline earth metal, and, more preferably, about 0.25 to about3.5 wt. %. Best results are obtained when this component is a compoundof lithium or potassium. The function of this component is to neutralizeany of the acidic material such as halogen which may have been used inthe preparation of the present catalyst so that the final catalyst innonacidic.

This alkali or alkaline earth component may be combined with the porouscarrier material in any manner known to those skilled in the art toresult in a relatively uniform dispersion of this component throughoutthe carrier material with consequential neutralization of any acidicsites which may be present therein. Typically good results are obtainedwhen it is combined by impregnation, coprecipitation, ion-exchange, andthe like procedures. The preferred procedure, however, involvesimpregnation of the carrier material either before, during, or after itis calcined, or before, during, or after the other metallic ingredientsare added to the carrier material. Best results are ordinarily obtainedwhen this component is added to the carrier material after the othermetallic components because the alkali metal or alkaline earth metalcomponent acts to neutralize the acidic materials used in the preferredimpregnation procedure for these metallic components. In fact, it ispreferred to add the platinum or palladium, iridium and tin or leadcomponents to the carrier material, oxidize the resulting composite in awet air stream at a high temperature (i.e. typically about 600° to 1000°F.), then treat the resulting oxidized composite with steam or a mixtureof air and steam at a relatively high temperature of about 800° to about1050° F. in order to remove at least a portion of any residual acidityand thereafter add the alkali metal or alkaline earth component.Typically, the impregnation of the carrier material with this componentis performed by contacting the carrier material with a solution of asuitable decomposable compound or salt of the desired alkali or alkalineearth metal. Hence, suitable compounds include the alkali metal oralkaline earth metal halides, sulfates, nitrates, acetates, carbonates,phosphates, and the like compounds. For example, excellent results areobtained by impregnating the carrier material after the other metalliccomponents have been combined therewith, with an aqueous solution oflithium nitrate or potassium nitrate.

Regarding the preferred amounts of the various metallic components ofthe subject catalyst, I have found it to be a good practice to specifythe amounts of the iridium component and the nickel component as afunction of the amount of the platinum or palladium component. On thisbasis, the amount of the iridium component is oridinarily selected sothat the atomic ratio of iridium to platinum or palladium metalcontained in the composite is about 0.1:1 to about 2:1, with thepreferred range being about 0.25:1 to about 1.5:1. Similarly, the amountof the tin or lead component is ordinarily selected to produce acomposite containing an atomic ratio of tin or lead to platinum orpalladium metal of about 0.05:1 to about 10:1, with the preferred rangebeing about 0.1:1 to about 1.5:1. Similarly, the amount of the alkali oralkaline earth component is ordinarily selected to produce a compositehaving an atomic ratio of alkali metal or alkaline earth metal toplatinum or palladium metal of about 5:1 to about 100:1 or more, withthe preferred range being about 10:1 to about 75:1.

Another significant parameter for the instant sulfided nonacidiccatalyst is the "total metals content" which is defined to be the sum ofthe platinum or palladium component, the iridium component, the tin orlead component, and the alkali or alkaline earth component, calculatedon an elemental metal basis. Good results are ordinarily obtained withthe subject catalyst when this parameter is fixed at a value of about0.2 to about 5 wt. %, with best results ordinarily achieved at a metalsloading of about 0.4 to about 4 wt. %.

Integrating the above discussion of each of the essential and preferredmetallic components of the catalytic composite used in the presentinvention, it is evident that an especially preferred sulfided nonacidiccatalytic composite comprises a combination of a platinum component, aniridium component, a tin or lead component, a sulfur component and analkali or alkaline earth component with an alumina carrier material inamounts sufficient to result in the composite containing, on anelemental basis, from about 0.05 to about 1 wt. % platinum, about 0.05to about 1 wt. % iridium, about 0.25 to about 3.5 wt. % of the alkalimetal or alkaline earth metal, about 0.05 to about 2 wt. % tin or leadand about 0.05 to about 0.5 wt. % sulfur.

Regardless of the details of how the components of the catalyst arecombined with the porous carrier material, the resulting multimetalliccomposite generally will be dried at a temperature of about 200° F. toabout 600° F. for a period of from about 2 to about 24 hours or more,and finally calcined or oxidized at a temperature of about 600° F. toabout 1100° F. in an air atmosphere for a period of about 0.5 to 10hours, preferably about 1 to about 5 hours, in order to convertsubstantially all the metallic components to the corresponding oxideform. When acidic components are present in any of the reagents used toeffect incorporation of any one of the components of the subjectcomposite, it is a good practice to subject the resulting composite to ahigh temperature treatment with steam or with a mixture of steam andair, either before, during or after this oxidation step in order toremove as much as possible of the undesired acidic component. Forexample, when the platinum or palladium component is incorporated byimpregnating the carrier material with chloroplatinic acid, it ispreferred to subject the resulting composite to a treatment with steam,or a mixture of steam and air, at a temperature of about 600° to 1100°F. in order to remove as much as possible of the undesired chloride.

It is an essential feature of the present invention that the resultantoxidized catalytic composite is subjected to a substantially water-free,reduction step prior to its use in the dehydrogenation of hydrocarbons.This step is designed to selectively reduce substantially all of theplatinum or palladium and iridium components to the correspondingmetals, while maintaining the tin or lead and alkali or alkaline earthcomponents in a positive oxidation state, and to insure a uniform andfinely divided dispersion of these metallic components throughout thecarrier material. It is a good practice to dry the oxidized catalystprior to this reduction step by passing a stream of dry air or nitrogenthrough same at a temperature of about 500° to 1100° F. at a GHSV ofabout 100 to 800hr.⁻¹ until the effluent stream contains less than 1000ppm H₂ O and preferably less than 500 ppm. Preferably substantially pureand dry hydrogen (i.e. less than 20 vol. ppm H₂ O) is used as thereducing agent in this step. The reducing agent is contacted with theoxidized catalyst at conditions including a temperature of about 800° F.to about 1200° F., a GHSV of about 300 to 1000hr.⁻¹ and a period of timeof about 0.5 to 10 hours effective to reduce substantially all of theplatinum or palladium and iridium components to their elemental metallicstate, while maintaining the tin or lead and alkali or alkaline earthcomponents in an oxidized state. This reduction treatment may beperformed in situ as part of a start-up sequence if precautions aretaken to predry the plant to a substantially water-free state and ifsubstantially water-free and hydrocarbon-free hydrogen is used.

A unique feature of the instant invention involves recognition that theresulting selectively reduced catalytic composite can be beneficiallysubjected to a presulfiding operation with a metal-sulfiding reagent.This step is designed to incorporate into the catalytic composite about0.01 to about 1 and, more preferably, about 0.05 to about 0.5 wt. %sulfur, calculated on an elemental basis. I have found that it iscritical to perform this presulfiding procedure prior to use of thecatalytic composite in the dehydrogenation of hydrocarbons and after theplatinum or palladium and iridium components are selectively reduced tothe corresponding elemental metallic state. The principal reason forthis requirement is that it ensures that the uniform distribution of themetallic components in the carrier material will not be adverselyaffected by the sulfur. Preferably, this presulfiding treatment takesplace in the presence of hydrogen and a suitable sulfur-containingdecomposable sulfiding reagent such as hydrogen sulfide, lower molecularweight mercaptans, organic sulfides, etc. Typically, this procedurecomprises treating the selectively reduced catalyst with a sulfiding gassuch as a mixture of hydrogen and hydrogen sulfide having about 10 molesof hydrogen per mole of hydrogen sulfide at conditions sufficient toeffect the incorporation of the desired amount of sulfur, generallyincluding a temperature ranging from about 50° F. up to about 1100° F.or more. It is generally a good practice to perform this presulfidingstep under substantially water-free conditions. The sulfided state ofthe instant catalyst can be maintained during the conversion process bycontinuously or periodically adding a sulfiding reagent to the reactorcontaining the catalyst in an amount corresponding to about 1 to 500 wt.ppm. of the hydrocarbon charge and preferably about 1 to 20 wt. ppm.

According to the method of the present invention, the dehydrogenatablehydrocarbon is contacted with this sulfided nonacidic multimetalliccatalytic composite in a dehydrogenation zone maintained atdehydrogenation conditions. This contacting may be accomplished by usingthe catalyst in a fixed bed system, a moving bed system, a fluidized bedsystem, or in a batch type operation; however, in view of the danger ofattrition losses of the valuable catalyst and of well-known operationaladvantages, it is preferred to use a fixed bed system. In this system,the hydrocarbon feed stream is preheated by any suitable heating meansto the desired reaction temperature and then passed into adehydrogenation zone containing a fixed bed of the catalyst previouslycharacterized. It is, of course, understood that the dehydrogenationzone may be one or more separate reactors with suitable heating meanstherebetween to insure that the desired conversion temperature ismaintained at the entrance to each reactor. It is also to be noted thatthe reactants may be contacted with the catalyst bed in either upward,downward, or radial flow fashion with the latter being preferred. Inaddition, it is to be noted that the reactants may be in the liquidphase, a mixed liquid-vapor phase, or a vapor phase when they contactthe catalyst, with best results obtained in the vapor phase.

Although hydrogen is the preferred diluent for use in the subjectdehydrogenation method, in some cases other art-recognized diluents maybe advantageously utilized such as steam, methane, carbon dioxide, andthe like diluents. Hydrogen is preferred because it serves thedual-function of not only lowering the partial pressure of thedehydrogenatable hydrocarbon, but also of suppressing the formation ofhydrogen-deficient, carbonaceous deposits on the catalytic composite.Ordinarily, hydrogen is utilized in amounts sufficient to insure ahydrogen to hydrocarbon mole ratio of about 1:1 to about 20:1, with bestresults obtained in the range of about 1.5:1 to about 10:1. The hydrogenstream charged to the dehydrogenation zone will typically be recycledhydrogen obtained from the effluent stream from this zone after asuitable hydrogen separation step. When utilizing hydrogen in theinstant process, improved results are obtained if water or awater-producing substance (such as an alcohol, ketone, ether, aldehyde,or the like oxygen-containing decomposable organic compound) is added tothe dehydrogenation zone in an amount calculated on the basis ofequivalent water, corresponding to about 1 to about 5000 wt. ppm. of thehydrocarbon charge stock, with about 1 to 1000 wt. ppm of water givenbest results. This water addition feature may be used on a continuous orintermittent basis to regulate activity and selectivity of the instantcatalyst.

Regarding the conditions utilized in the process of the presentinvention, these are generally selected from the dehydrogenationconditions well known to those skilled in the art for the particulardehydrogenatable hydrocarbon which is charged to the process. Morespecifically, suitable conversion temperatures are selected from therange of about 700 to about 1200° F. with a value being selected fromthe lower portion of this range for the more easily dehydrogenatedhydrocarbons such as the long chain normal paraffins and from the higherportion of this range for the more difficulty dehydrogenatedhydrocarbons such as propane, butane, and the like hydrocarbons. Forexample, for the dehydrogenation of C₆ to C₃₀ normal paraffins, bestresults are ordinarily obtained at a temperature of about 800° to about950° F. The pressure utilized is ordinarily selected at a value which isas low as possible consistent with the maintenance of catalyst stabilityand is usually about 0.1 to about 10 atmospheres with best resultsordinarily obtained in the range of about 0.5 to about 3 atmospheres. Inaddition, a liquid hourly space velocity (calculated on the basis of thevolume amount, as a liquid, of hydrocarbon charged to thedehydrogenation zone per hour divided by the volume of the catalyst bedutilized) is selected from the range of about 1 to about 40 hr.⁻ 1, withbest results for the dehydrogenation of long chain normal paraffinstypically obtained at a relatively high space velocity of about 25 to 35hr.⁻¹.

Regardless of the details concerning the operation of thedehydrogenation step, an effluent stream will be withdrawn therefrom.This effluent will usually contain unconverted dehydrogenatablehydrocarbons, hydrogen, and products of the dehydrogenation reaction.This stream is typically cooled and passed to a hydrogen-separating zonewherein a hydrogen-rich vapor phase is allowed to separate from ahydrocarbon-rich liquid phase. In general, it is usually desired torecover the unreacted dehydrogenatable hydrocarbon from thishydrocarbon-rich liquid phase in order to make the dehydrogenationprocess economically attractive. This recovery operation can beaccomplished in any suitable manner known to the art such as by passingthe hydrocarbon-rich liquid phase through a bed of suitable adsorbentmaterial which has the capability to selectively retain thedehydrogenated hydrocarbons contained therein or by contacting same witha solvent having a high selectivity for the dehydrogenated hydrocarbon,or by a suitable fractionation scheme where feasible. In the case wherethe dehydrogenated hydrocarbon is a mono-olefin, suitable adsorbentshaving this capability are activated silica gel, activated carbon,activated alumina, various types of specially prepared zeoliticcrystalline aluminosilicates, molecular sieves, and the like adsorbents.In another typical case, the dehydrogenated hydrocarbons can beseparated from the unconverted dehydrogenatable hydrocarbons byutilizing the inherent capability of the dehydrogenated hydrocarbons toeasily enter into several well-known chemical reactions such asalkylation, oligomerization, halogenation, sulfonation, hydration,oxidation, and the like reactions. Irrespective of how thedehydrogenated hydrocarbons are separated from the unreactedhydrocarbons, a stream containing the unreacted dehydrogenatablehydrocarbons will typically be recovered from this hydrocarbonseparation step and recycled to the dehydrogenation step. Likewise, thehydrogen phase present in the hydrogen-separating zone will be withdrawntherefrom, a portion of it vented from the system in order to remove thenet hydrogen make, and the remaining portion is typically recycledthrough suitable compressing means to the dehydrogenation step in orderto provide diluent hydrogen therefor.

In a preferred embodiment of the present invention wherein long chainnormal paraffin hydrocarbons are dehydrogenated to the correspondingnormal mono-olefins, a preferred mode of operation of this hydrocarbonrecovery step involves an alkylation reaction. In this mode, thehydrocarbon-rich liquid phase withdrawn from the hydrogen-separatingzone is combined with a stream containing an alkylatable aromatic andthe resulting mixture passed to an alkylation zone containing a suitablehighly acid catalyst such as an anhydrous solution of hydrogen fluoride.In the alkylation zone the mono-olefins react with alkylatable aromaticwhile the unconverted normal paraffins remain substantially unchanged.The effluent stream from the alkylation zone can then be easilyseparated, typically by means of a suitable fractionation system, toallow recovery of the unreacted normal paraffins. The resulting streamof unconverted normal paraffins is then usually recycled to thedehydrogenation step of the present invention.

The following working examples are introduced to illustrate further thenovelty, mode of operation, utility, and benefits associated with thedehydrogenation method and sulfided nonacidic multimetallic catalyst ofthe present invention. These examples of specific embodiments of thepresent invention are intended to be illustrative rather thanrestrictive.

These examples are all performed in a laboratory scale dehydrogenationplant comprising a reactor, a hydrogen separating zone, heating means,cooling means, pumping means, compressing means, and the likeconventional equipment. In this plant, the feed stream containing thedehydrogenatable hydrocarbon is combined with a hydrogen streamcontaining water in an amount corresponding to about 100 wt. ppm. of thehydrocarbon feed and the resultant mixture heated to the desiredconversion temperature, which refers herein to the temperaturemaintained at the inlet to the reactor. The heated mixture is thenpassed into contact with the sulfided multimetallic catalyst which ismaintained as a fixed bed of catalyst particles in the reactor. Thepressures reported herein are recorded at the outlet from the reactor.An effluent stream is withdrawn from the reactor, cooled, and passedinto the hydrogen-separating zone wherein a hydrogen gas phase separatesfrom a hydrogen-rich liquid phase containing dehydrogenatedhydrocarbons, unconverted dehydrogenatable hydrocarbons, and a minoramount of side products of the dehydrogenation reaction. A portion ofthe hydrogen-rich gas phase is recovered as excess recycle gas with theremaining portion being continuously recycled, after water addition asneeded, through suitable compressing means to the heating zone asdescribed above. The hydrocarbon-rich liquid phase from the separatingzone is withdrawn therefrom and subjected to analysis to determineconversion and selectivity for the desired dehydrogenated hydrocarbon aswill be indicated in the Examples. Conversion numbers of thedehydrogenatable hydrocarbon reported herein are all calculated on thebasis of disappearance of the dehydrogenatable hydrocarbon and areexpressed in mole percent. Similarly, selectivity numbers are reportedon the basis of moles of desired hydrocarbon produced per 100 moles ofdehydrogenatable hydrocarbon converted.

All of the catalysts utilized in these examples are prepared accordingto the following general method with suitable modification instoichiometry to achieve the compositions reported in each example.First, an alumina carrier material comprising 1/16 inch spheres havingan apparent bulk density of about 0.3 g/cc is prepared by: forming analumina hydroxyl chloride sol by dissolving substantially pure aluminumpellets in a hydrochloric acid solution, adding hexamethylenetetramineto the resulting alumina sol, gelling the resulting solution by droppingit into an oil bath to form spherical particles of an alumina hydrogel,aging, and washing the resulting particles with an ammoniacal solutionand finally drying, calcining, and steaming the aged and washedparticles to form spherical particles of gamma-alumina containingsubstantially less than 0.1 wt. % combined chloride. Additional detailsas to this method of preparing this alumina carrier material are givenin the teachings of U.S. Pat. No. 2,620,314.

The resulting gamma-alumina particles are then contacted at impregnationconditions with an aqueous impregnation solution containingchloroplatinic acid, stannic chloride or lead nitrate, chloroiridicacid, and nitric acid in amounts sufficient to yield a finalmultimetallic catalytic composite containing a uniform dispersion of thedesired amounts of platinum, tin or lead and iridium. The nitric acid isutilized in an amount of about 5 wt. % of the alumina particles. Inorder to ensure a uniform dispersion of the metal moieties in thecarrier material, the impregnation solution is maintained in contactwith the carrier material particles for about 1/2 hour at a temperatureof about 70° F. with constant agitation. The impregnated spheres arethen dried at a temperature of about 225° F. for about an hour andthereafter calcined or oxidized in an air atmosphere containing about 5to 25 vol. % H₂ O at a temperature of about 500° F. to about 1000° F.for about 2 to 10 hours effective to convert all of the metalliccomponents to the corresponding oxide forms. In general, it is a goodpractice to thereafter treat the resulting oxidized particles with anair stream containing about 10 to about 30% steam at a temperature ofabout 800° F. to about 1000° F. for an additional period of about 1 toabout 5 hours in order to reduce any residual combined chloridecontained in the catalyst to a value of less than 0.5 wt. % andpreferably less than 0.2 wt. %.

Regarding the alkali or alkaline earth component, this component isadded to the resulting oxidized and steam-treated multimetallic catalystin a separate impregnation step. This second impregnation step involvescontacting the oxidized multimetallic catalyst with an aqueous solutionof a suitable decomposable salt of the alkali or alkaline earthcomponent under conditions selected to result in a uniform dispersion ofthis component in the carrier material. For the catalyst utilized in thepresent examples, the salt is either lithium nitrate or potassiumnitrate. The amount of the salt of the alkali metal utilized is chosento result in a final catalyst having the desired nonacidiccharacteristics. The resulting alkali or alkaline earth impregnatedparticles are then preferably dried, oxidized, and steamed in an airatmosphere in much the same manner as is described above following thefirst impregnation step. In some cases, it is possible to combine bothof these impregnation steps into a single step, thereby significantlyreducing the time and complexity of the catalyst manufacturingprocedure.

The resulting doubly impregnated catalyst is thereafter subjected to adrying step which involves contacting the oxidized particles with a dryair stream at a temperature of about 1050° F., a GHSV of 300 hr.⁻¹, fora period of about 10 hours. The dried oxidized catalyst is then purgedwith a dry nitrogen stream and thereafter selectively reduced bycontacting with a dry hydrogen stream at conditions including atemperature of about 870° F., atmospheric pressure and a gas hourlyspace velocity of about 500 hr.⁻¹ for a period of about 1 to 10 hours,effective to reduce substantially all of the platinum and iridiumcomponents to the corresponding elemental metals while maintaining thetin or lead and alkali or alkaline earth component in a positiveoxidation state.

The resulting selectively reduced catalyst particles are then contactedwith a sulfiding gas comprising a mixture of a mixture of H₂ S and H₂ ina mole ratio of 1:10 at a temperature of about 1050° F., atmosphericpressure and a GHSV of about 800 hr.⁻¹ for a period of about 1/2 houreffective to produce a sulfided catalyst containing, on an elementalbasis, about 0.2 wt. % sulfur.

EXAMPLE I

The reactor is loaded with 100 cc of a sulfided nonacidic catalystcontaining, on an elemental basis, 0.25 wt. % platinum, 0.25 wt. %iridium, 0.5 wt. % lithium, 0.3 wt. % tin, 0.2 wt. % sulfur, and lessthan 0.15 wt. % chloride. The feed stream utilized is commercial gradeisobutane containing 99.7 wt. % isobutane and 0.3 wt. % normal butane.The feed stream is contacted with the catalyst at a temperature of 1065°F., a pressure of 10 psig., a LHSV of 4.0 hr.⁻¹, and a hydrogen tohydrocarbon mole ratio of 2:1. The dehydrogenation plant is lined-out atthese conditions and a 20 hour test period commenced. The hydrocarbonproduct stream from the plant is continuously analyzed by GLC (gasliquid chromatography) and a high conversion of isobutane is observedwith a high selectivity for isobutylene.

EXAMPLE II

The sulfided nonacidic catalyst contains, on an elemental basis, 0.375wt. % platinum, 0.2 wt. % iridium, 0.1 wt. % lead, 0.2 wt. % sulfur, 0.6wt. % lithium, and 0.15 wt. % combined chloride. The feed stream iscommercial grade normal dodecane. The dehydrogenation reactor isoperated at a temperature of 870° F., a pressure of 10 psig., a LHSV of32 hr.⁻¹, and a hydrogen to hydrocarbon mole ratio of 8:1. After aline-out period, a 20 hour test period is performed during which theaverage conversion of the normal dodecane is maintained at a high levelwith a selectivity for normal dodecane of about 90%.

EXAMPLE III

The sulfided nonacidic catalyst is the same as utilized in Example II.The feed stream is normal tetradecane. The conditions utilized are atemperature of 840° F., a pressure of 20 psig., a LHSV of 32 hr.⁻¹, anda hydrogen to hydrocarbon mole ratio of 8:1. After a line-out period, a20 hour test shows an average conversion of about 12% and a selectivityfor normal tetradecene of about 90%.

EXAMPLE IV

The sulfided nonacidic catalyst contains, on an elemental basis, 0.25wt. % platinum, 0.125 wt. % iridium, 0.4 wt. % tin, 0.2 wt. % sulfur,and 0.6 wt. % lithium, with combined chloride being less than 0.2 wt. %.The feed stream is substantially pure cyclohexane. The conditionsutilized are a temperature of 950° F., a pressure of 100 psig., a LHSVof 3.0 hr.⁻¹, and a hydrogen to hydrocarbon mole ratio of 5:1. After aline-out period, a 20 hour test is performed with almost quantitativeconversion of cyclohexane to benzene and hydrogen.

EXAMPLE V

The sulfided nonacidic catalyst contains, on an elemental basis, 0.2 wt.% platinum, 0.2 wt. % iridium, 0.4 wt. % tin, 0.2 wt. % sulfur, 1.5 wt.% potassium, and less than 0.2 wt. % combined chloride. The feed streamis commercial grade ethylbenzene. The conditions utilized are a pressureof 15 psig., a LHSV of 32 hr.⁻¹, a temperature of 1050° F., and ahydrogen to hydrocarbon mole ratio of 8:1. During a 20 hour test period,85% or more of equilibrium conversion of the ethylbenzene is observed.The selectivity for styrene is about 95%.

It is intended to cover by the following claims, all changes andmodifications of the above disclosure of the present invention whichwould be self-evident to a man of ordinary skill in thecatalyst-formulation art or in the hydrocarbon dehydrogenation art.

I claim as my invention:
 1. A method for dehydrogenating adehydrogenatable hydrocarbon comprising contacting the hydrocarbon atdehydrogenation conditions with a sulfided nonacidic catalytic compositecomprising a porous carrier material consisting essentially of, on anelemental basis, about 0.01 to about 2 wt. % platinum or palladium,about 0.01 to about 2 wt. % iridium, about 0.1 to about 5 wt. % alkalimetal or alkaline earth metal, about 0.01 to about 5 wt. % tin or lead,and about 0.01 to about 1 wt. % sulfur; wherein the platinum orpalladium, iridium, alkali metal or alkaline earth metal and tin or leadare uniformly dispersed throughout the porous carrier material; whereinsubstantially all of the platinum or palladium and iridium are presentin a sulfided state or in a mixture of the elemental metallic state andthe sulfided state; wherein substantially all of the tin or lead andalkali metal or alkaline earth metal are present in an oxidation stateabove that of the elemental metal; and wherein the composite has beensulfided, prior to contact with any hydrocarbon and after substantiallyall of the platinum or palladium and iridium contained therein have beenreduced to the corresponding elemental metallic state, by treatment witha sulfiding gas at conditions selected to incorporate about 0.01 toabout 1 wt. % sulfur.
 2. A dehydrogenation method as defined in claim 1wherein the porous carrier material is a refractory inorganic oxide. 3.A dehydrogenation method as defined in claim 2 wherein the refractoryinorganic oxide is alumina.
 4. A dehydrogenation method as defined inclaim 1 wherein the alkali metal or alkaline earth metal is potassium.5. A dehydrogenation method as defined in claim 1 wherein the alkalimetal or alkaline earth metal is lithium.
 6. A dehydrogenation method asdefined in claim 1 wherein the sulfiding gas is a mixture of hydrogenand hydrogen sulfide.
 7. A dehydrogenation method as defined in claim 1wherein the composite consisting essentially of, on an elemental basis,about 0.05 to about 1 wt. % platinum or palladium, about 0.05 to about 1wt. % iridium, about 0.25 to about 3.5 wt. % alkali metal or alkalineearth metal, about 0.05 to about 2 wt. % tin or lead and about 0.05 toabout 0.5 wt. % sulfur.
 8. A dehydrogenation method as defined in claim1 wherein the metals contents thereof is adjusted so that the atomicratio of iridium to platinum or palladium is about 0.1:1 to about 2:1,the atomic ratio of alkali metal or alkaline earth metal to platinum orpalladium is about 5:1 to about 100:1 and the atomic ratio of tin orlead to platinum or palladium is about 0.05:1 to about 10:1.
 9. Adehydrogenation method as defined in claim 1 wherein substantially allof the tin or lead is present as tin oxide or lead oxide.
 10. A methodas defined in claim 1 wherein the dehydrogenatable hydrocarbon isadmixed with hydrogen when it contacts the catalytic composite.
 11. Amethod as defined in claim 1 wherein the dehydrogenatable hydrocarbon isan aliphatic hydrocarbon compound containing 2 to 30 carbon atoms permolecule.
 12. A method as defined in claim 1 wherein thedehydrogenatable hydrocarbon is a normal paraffin hydrocarbon containingabout 4 to 30 carbon atoms per molecule.
 13. A method as defined inclaim 1 wherein the dehydrogenatable hydrocarbon is a normal paraffinhydrocarbon containing about 10 to about 18 carbon atoms per molecule.14. A method as defined in claim 1 wherein the dehydrogenatablehydrocarbon is an alkylaromatic, the alkyl group of which contains about2 to 6 carbon atoms.
 15. A method as defined in claim 1 wherein thedehydrogenatable hydrocarbon is a naphthene.
 16. A method as defined inclaim 1 wherein the dehydrogenation conditions include a temperature ofabout 700 to about 1200° F., a pressure of about 0.1 to about 10atmospheres, an LHSV of about 1 to 40 hr.⁻¹, and a hydrogen tohydrocarbon mole ratio of about 1:1 to about 20:1.
 17. A method asdefined in claim 1 wherein the contacting is performed in the presenceof water or a water-producing substance in an amount corresponding toabout 1 to about 5000 wt ppm. based on hydrocarbon charge.